Transposagen is developing an innovative mammalian random mutagenesis system that uses an L1 retrotransposon for direct germ-line mutagenesis. Transposagen's goal is to produce "mutator rats". In these rats, mutagensis will occur in sperm and some offspring will contain single gene disruptions. We will use the mouse to optimize and validate our system because of the much higher cost in producing transgenic rats. We have developed "mutator mice" containing a marked L1 transgene capable of germ-line insertional mutagenesis. The focus of this proposal is to validate the Transposagen random mutagenesis system as a tool for functional genomics. Phase I of this project includes characterization of the mutator mice. Specific aim 1 is to determine the frequency of insertional mutagenesis in the sperm of mutator mice. Specific aim 2 is to determine the percentage of insertions that insert into genes. Specific aim 3 is to determine the efficiency of gene disruption. Phase II of the project will use the information gained from the Phase I mouse studies to create mutator rats. L1 elements are present in all mammals and a human L1 element is capable of high-level retrotransposition in human, mouse, hamster, feline, and even quail cells. Therefore, our findings in mice from this study should extrapolate directly to rats. Transposagen's random mutagenesis system could utlimately be adapted for use in any mammal. Mutator mice and rats will substantially aid drug discovery programs by producing animal models for new drug targets. [unreadable] [unreadable]